Multicomponent polyamide-block copolymer-polymer blends

ABSTRACT

A multicomponent polymer blend composition is prepared by intimately mixing a polyamide, a selectively hydrogenated monoalkenyl arene-diene block copolymer, and at least one dissimilar engineering thermoplastic resin under such conditions that at least two of the polymers form at least partial continuous network phases which interlock with the other polymer networks and therefore results in a desirable balance of properties.

This application is a continuation-in-part of applicants copendingapplication Ser. No. 693,462, filed June 7, 1976, now U.S. Pat. No.4,041,103.

BACKGROUND OF THE INVENTION

Engineering thermoplastics are a group of polymers that possess abalance of properties comprising strength, stiffness, impact resistance,and long term dimensional stability that make them useful as structuralmaterials. Engineering thermoplastics are especially attractive asreplacements for metals because of the reduction in weight that canoften be achieved as, for example, in automotive applications.

For a particular application, a single plastic may not offer thecombination of properties desired and, therefore, means to correct thisdeficiency are of interest. One particularly appealing route is throughblending together two or more polymers (which individually have theproperties sought) to give a material with the desired combination ofproperties. This approach has been successful in limited cases such asin the improvement of impact resistance for plastic, e.g. polystyrene,polypropylene, poly(vinyl chloride), etc., using special blendingprocedures or additives for this purpose. However, in general, blendingof plastics has not been a successful route to enable one to combineinto a single material the desirable individual characteristics of twoor more polymers. Instead, it has often been found that such blendingresults in combining the worst features of each with the result being amaterial of such poor properties as not to be of any practical orcommercial value. The reasons for this failure are rather wellunderstood and stem in part from the fact that thermodynamics teachesthat most combinations of polymer pairs are not miscible, although anumber of notable exceptions are known. More importantly, most polymersadhere poorly to one another. As a result, the interfaces betweencomponent domains (a result of their immiscibility) represent areas ofsevere weakness in blends and, therefore, provide natural flaws andcracks which result in facile mechanical failure. Because of this, mostpolymer pairs are said to be "incompatible". In some instances the termcompatibility is used synonymously with miscibility, however,compatibility is used here in a more general way that describes theability to combine two polymers together for beneficial results and mayor may not connote miscibility.

One method which may be used to circumvent this problem in polymerblends is to "compatibilize" the two polymers by blending in a thirdcomponent, often referred to as a "compatibilizing agent", thatpossesses a dual solubility nature for the two polymers to be blended.Examples of this third component most typically are obtained in block orgraft copolymers. As a result of this characteristic, this agent locatesat the interface between components and greatly improves interphaseadhesion and therefore increases stability to gross phase separation.

The present invention covers a means to stabilize multipolymer blendsthat is independent of the prior art compatibilizing process and is notrestricted to the necessity for restrictive dual solubilitycharacteristics. The materials used for this purpose are special blockcopolymers capable of thermally reversible selfcross-linking. Theiraction in the present invention is not that visualized by the usualcompatibilizing concept as evidenced by the general ability of thesematerials to perform similarly for a wide range of blend componentswhich do not conform to the solubility requirements of the previousconcept.

SUMMARY OF THE INVENTION

A novel composition has now been found that exhibits excellentdimensional stability and integrity. The composition broadly comprisesthe admixture obtained by intimately mixing about 4 to about 40 parts byweight of a block copolymer, about 5 to about 48 parts by weight of atleast one dissimilar engineering thermoplastic, and a polyamide in aweight ratio of polyamide to dissimilar engineering thermoplastic ofgreater than 1:1 so as to form a polyblend wherein at least two of thepolymers form at least partial continuous interlocked networks with eachother, and wherein:

(a) said block copolymer comprises at least two monoalkenyl arenepolymer end blocks A and at least one substantially completelyhydrogenated conjugated diene polymer mid block B, said block copolymerhaving an 8 to 55 percent by weight monoalkenyl arene polymer blockcontent, each polymer block A having an average molecular weight ofbetween about 5,000 and about 125,000, and each polymer block B havingan average molecular weight of between about 10,000 and about 300,000;

(b) said polyamide has a number average molecular weight in excess ofabout 10,000; and

(c) said dissimilar engineering thermoplastic resin is capable offorming a continuous network structure, and is selected from the groupconsisting of polyolefins, thermoplastic polyesters, poly(aryl ethers),poly(aryl sulfones), polycarbonates, acetal resins, thermoplasticpolyurethanes, halogenated thermoplastics, and nitrile barrier resins.

The block copolymer of the instant invention effectively acts as amechanical or structural stabilizer which interlocks the various polymerstructure networks and prevents the consequent separation of thepolymers during processing and their subsequent use. As defined morefully hereinafter, the resulting structure of the instant polyblend(short for "polymer blend") is that of at least two partial continuousinterlocking networks. This interlocked structure results in adimensionally stable polyblend that will not delaminate upon processingand subsequent use.

To produce stable blends it is necessary that at least two of thepolymers have at least partial continuous networks which interlock witheach other. Preferably, the block copolymer and at least one otherpolymer have partial continuous interlocking network structures. In anideal situation all of the polymers would have complete continuousnetworks which interlock with each other. A partial continuous networkmeans that a portion of the polymer has a continuous network phasestructure while the other portion has a disperse phase structure.Preferably a major proportion (greater than 50% by weight) of thepartial continuous network is continuous. As can be readily seen, alarge variety of blend structures is possible since the structure of thepolymer in the blend may be completely continuous, completely disperse,or partially continuous and partially disperse. Further yet, thedisperse phase of one polymer may be dispersed in a second polymer andnot in a third polymer. To illustrate some of the structures, thefollowing lists the various combinations of polymer structures possiblewhere all structures are complete as opposed to partial structures.Three polymers (A, B and C) are involved. The subscript "c" signifies acontinuous structure while the subscript "d" signifies a dispersestructure. Thus, the designation "A_(c) B" means that polymer A iscontinuous with polymer B, and the designation "B_(d) C" means thatpolymer B is disperse in polymer C, etc.

    ______________________________________                                        A.sub.c B    A.sub.c C   B.sub.c C                                            A.sub.d B    A.sub.c C   B.sub.c C                                            A.sub.c B    A.sub.c C   B.sub.d C                                            B.sub.d A    A.sub.c C   B.sub.c C                                            B.sub.d C    A.sub.c B   A.sub.c C                                            C.sub.d A    A.sub.c B   A.sub.c C                                            C.sub.d B    A.sub.c B   A.sub.c C                                            ______________________________________                                    

Through practice of the present invention, it is possible to preparepolyblends that possess a much improved balance of properties ascompared to the individual properties of the separate polymers. Forexample, the present invention permits the blending of a large amount ofa polyamide with a smaller amount of a more expensive engineeringthermoplastic, such as poly(butylene terephthalate), resulting in apolymer blend that retains much of the desirable properties of the moreexpensive engineering thermoplastic at a fraction of the cost.

It is particularly surprising that even just small amounts of thepresent block copolymer are sufficient to stabilize the structure of thepolymer blend over very wide relative concentrations. For example, aslittle as four parts by weight of the block copolymer is sufficient tostabilize a blend of 5 to 90 parts by weight polyamide with 90 to 5parts by weight of a dissimilar engineering thermoplastic.

In addition, it is also surprising that the instant block copolymers areuseful in stabilizing polymers of such a wide variety and chemicalmakeup. As explained more fully hereinafter, the instant blockcopolymers have this ability to stabilize a wide variety of polymersover a wide range of concentrations since they are oxidatively stable,possess essentially an infinite viscosity at zero shear stress, andretain network or domain structure in the melt.

Another significant aspect of the present invention is that the ease ofprocessing and forming the various polyblends is greatly improved byemploying the instant block copolymers as stabilizers.

RELATIONSHIP TO OTHER APPLICATIONS

This application is related to patent application Ser. No. 776,174,filed Feb. 7, 1977, having a common assignee and common inventors.

DETAILED DESCRIPTION OF THE INVENTION

A. Block Copolymer

The block copolymers employed in the present invention may have avariety of geometrical structures, since the invention does not dependon any specific geometrical structure, but rather upon the chemicalconstitution of each of the polymer blocks. Thus, the structures may belinear, radial or branched so long as each copolymer has at least twopolymer end blocks A and at least one polymer mid block B as definedabove. Methods for the preparation of such polymers are known in theart. Particular reference will be made to the use of lithium basedcatalysts and especially lithium-alkyls for the preparation of theprecursor polymers (polymers before hydrogenation). U.S. Pat. No.3,595,942 not only describes some of the polymers of the instantinvention but also describes suitable methods for their hydrogenation.The structure of the polymers is determined by their methods ofpolymerization. For example, linear polymers result by sequentialintroduction of the desired monomers into the reaction vessel when usingsuch initiators as lithium-alkyls or dilithiostilbene and the like, orby coupling a two segment block copolymer with a difunctional couplingagent. Branched structures, on the other hand, may be obtained by theuse of suitable coupling agents having a functionality with respect tothe precursor polymers of three or more. Coupling may be effected withmultifunctional coupling agents such as dihaloalkanes or -alkenes anddivinyl benzene as well as certain polar compounds such as siliconhalides, siloxanes or esters of monohydric alcohols with carboxylicacids. The presence of any coupling residues in the polymer may beignored for an adequate description of the polymers forming a part ofthe compositions of this invention. Likewise, in the generic sense, thespecific structures also may be ignored. The invention appliesespecially to the use of selectively hydrogenated polymers having theconfiguration before hydrogenation of the following typical species:

polystyrene-polybutadiene-polystyrene (SBS)

polystyrene-polyisoprene-polystyrene (SIS)

poly(alpha-methylstyrene)-polybutadienepoly(alpha-methylstyrene) and

poly(alpha-methylstyrene)-polyisoprenepoly(alpha-methystyrene)

It will be understood that both blocks A and B may be either homopolymeror random copolymer blocks as long as each block predominates in atleast one class of the monomers characterizing the blocks and as long asthe A blocks individually predominate in monoalkenyl arenes and the Bblocks individually predominate in dienes. The term "monoalkenyl arene"will be taken to include especially styrene and its analogs and homologsincluding alphamethylstyrene and ring-substituted styrenes, particularlyring-methylated styrenes. The preferred monoalkenyl arenes are styreneand alphamethylstyrene, and styrene is particularly preferred. Theblocks B may comprise homopolymers of butadiene or isoprene andcopolymers of one of these two dienes with a monoalkenyl arene as longas the blocks B predominate in conjugated diene units. When the monomeremployed is butadiene, it is preferred that between about 35 and about55 mol percent of the condensed butadiene units in the butadiene polymerblock have 1,2 configuration. Thus, when such a block is hydrogenated,the resulting product is, or resembles, a regular copolymer block ofethylene and butene-1 (EB). If the conjugated diene employed isisoprene, the resulting hydrogenated product is or resembles a regularcopolymer block of ethylene and propylene (EP).

Hydrogenation of the precursor block copolymers is preferably effectedby use of a catalyst comprising the reaction products of an aluminumalkyl compound with nickel or cobalt carboxylates or alkoxides undersuch conditions as to substantially completely hydrogenate at least 80%of the aliphatic double bonds while hydrogenating no more than about 25%of the alkenyl arene aromatic double bonds. Preferred block copolymersare those where at least 99% of the aliphatic double bonds arehydrogenated while less than 5% of the aromatic double bonds arehydrogenated.

The average molecular weights of the individual blocks may vary withincertain limits. In most instances, the monoalkenyl arene blocks willhave number average molecular weights in the order of 5,000-125,000,preferably 7,000-60,000 while the conjugated diene blocks either beforeor after hydrogenation will have average molecular weights in the orderof 10,000-300,000, preferably 30,000-150,000. The total averagemolecular weight of the block copolymer is typically in the order of25,000 to about 350,000, preferably from about 35,000 to about 300,000.These molecular weights are most accurately determined by tritiumcounting methods or osmotic pressure measurements.

The proportion of the monoalkenyl arene blocks should be between about 8and 55% by weight at the block copolymer, preferably between about 10and 30% by weight.

While the average molecular weight of the individual blocks is notcritical, at least within the above specified limits, it is important toselect the type and total molecular weight of the block copolymer inorder to ensure the compatibility necessary to get the interlockingnetwork under the chosen blending conditions. As discussed more fullyhereinafter, best results are obtained when the viscosity of the blockcopolymer and the engineering thermoplastic resins are substantially thesame at the temperature used for blending and processing. In someinstances, matching of the viscosity of the block copolymer portion andthe resin portions are best achieved by using two or more blockcopolymers or resins. For example, a blend of two block copolymershaving different molecular weights or a blend of a hydrogenated SBS andhydrogenated SIS polymers may be employed.

Matching of the viscosity of the block copolymer portion and thepolyolefin and engineering thermoplastic resin portions may also beaccomplished by adding supplemental blending components such ashydrocarbon oils and other resins. These supplementary components may beblended with the block copolymer portion, the polyamide portion, theengineering thermoplastic resin portion, or all portions, but it ispreferred to add the additional components to the block copolymerportion. This pre-blended block copolymer composition is then intimatelymixed with the polyamide and the engineering thermoplastic resin to formcompositions according to the present invention.

The types of oils useful in the practice of this invention are thosepolymer extending oils ordinarily used in the processing of rubber andplastics, e.g. rubber compounding oils. Especially preferred are thetypes of oil that are compatible with the elastomeric segment of theblock copolymer. While oils of higher aromatics content aresatisfactory, those petroleum-based white oils having low volatility andless than 50% aromatics content as determined by the clay gel method oftentative ASTM method D 2007 are particularly preferred. The oils shouldadditionally have low volatility, preferably having an initial boilingpoint above 500° F. The amount of oil employed varies from about 0 toabout 100 phr (parts by weight per hundred parts by weight rubber, orblock copolymer as in this case), preferably about 5 to about 30 phr.

The additional resins employed in matching viscosities are flowpromoting resins such as alpha-methylstyrene resins, and end blockplasticizing resins. Suitable end block plasticizing resins includecoumarone-indene resins, vinyl toluene-alpha-methylstyrene copolymers,polyindene resins, and low molecular weight polystyrene resins. See U.S.Pat. No. 3,917,607. The amount of additional resin employed varies fromabout 0 to about 100 phr, preferably about 5 to about 25 phr.

B. Polyamides

By polyamide is meant a condensation product which contains recurringaromatic and/or aliphatic amide groups as integral parts of the mainpolymer chain, such products being known generically as "nylons". Thesemay be obtained by polymerizing a monoaminomonocarboxylic acid or aninternal lactam thereof having at least two carbon atoms between theamino and carboxylic acid groups; or by polymerizing substantiallyequimolar proportions of a diamine which contains at least two carbonatoms between the amino groups and a dicarboxylic acid; or bypolymerizing a monoaminocarboxylic acid or an internal lactam thereof asdefined above together with substantially equimolecular proportions of adiamine and a dicarboxylic acid. The dicarboxylic acid may be used inthe form of a functional derivative thereof, for example an ester.

The term "substantially equimolecular proportions" (of the diamine andof the dicarboxylic acid) is used to cover both strict equimolecularproportions and the slight departures therefrom which are involved inconventional techniques for stabilizing the viscosity of the resultantpolyamides.

As examples of the said monoaminomonocarboxylic acids or lactams thereofthere may be mentioned those compounds containing from 2 to 16 carbonatoms between the amino and carboxylic acid groups, said carbon atomsforming a ring with the --CO·NH-- group in the case of a lactam. Asparticular examples of aminocarboxylic acids and lactams there may bementioned ε-aminocaproic acid, butyrolactam, pivalolactam, caprolactam,capryl-lactam, enantholactam, undecanolactam, dodecanolactam and 3- and4-amino benzoic acids.

Examples of the said diamines are diamines of the general formula H₂N(CH₂)_(n) NH₂ wherein n is an integer of from 2 to 16, such astrimethylenediamine, tetramethylenediamine, pentamethylenediamine,octamethylenediamine, decamethylenediamine, dodecamethylenediamine,hexadecamethylenediamine, and especially hexamethylenediamine.

C-alkylated diamines, e.g. 2,2-dimethylpentamethylenediamine and 2,2,4-and 2,4,4-trimethylhexamethylenediamine are further examples. Otherdiamines which may be mentioned as examples are aromatic diamines, e.g.p-phenylenediamine, 4,4'-diaminodiphenyl sulphone, 4,4'-diaminodiphenylether and 4,4'-diaminodiphenyl sulphone, 4,4'-diaminodiphenyl ether and4,4'-diaminodiphenylmethane; and cycloaliphatic diamines, for examplediaminodicyclohexylmethane.

The said dicarboxylic acids may be aromatic, for example isophthalic andterephthalic acids. Preferred dicarboxylic acids are of the formulaHOOC·Y·COOH wherein Y represents a divalent aliphatic radical containingat least 2 carbon atoms, and examples of such acids are sebacic acid,octadecanedioc acid, suberic acid, azelaic acid, undecanedioic acid,glutaric acid, pimelic acid, and especially adipic acid. Oxalic acid isalso a preferred acid.

Specifically the following polyamides may be incorporated in thethermoplastic polymer blends of the invention:

polyhexamethylene adipamide (nylon 6:6)

polypyrrolidone (nylon 4)

polycaprolactam (nylon 6)

polyheptolactam (nylon 7)

polycapryllactam (nylon 8)

polynonanolactam (nylon 9)

polyundecanolactam (nylon 11)

polydodecanolactam (nylon 12)

polyhexamethylene azelaiamide (nylon 6:9)

polyhexamethylene sebacamide (nylon 6:10)

polyhexamethylene isophthalamide (nylon 6:iP)

polymetaxylylene adipamide (nylon MXD:6)

polyamide of hexamethylenediamine and n-dodecanedioic acid (nylon 6:12)

polyamide of dodecamethylenediamine and

n-dodecanedioic acid (nylon 12:12)

Nylon copolymers may also be used, for example copolymers of thefollowing:

hexamethylene adipamide/caprolactam (nylon 6:6/6)

hexamethylene adipamide/hexamethylene-isophthalamide (nylon 6:6/6ip)

hexamethylene adipamide/hexamethylene-terephthalamide (nylon 6:6/6T)

trimethylhexamethylene oxamide/hexamethylene oxamide (nylontrimethyl-6:2/6:2)

hexamethylene adipamide/hexamethylene-azelaiamide (nylon 6:6/6:9)

hexamethylene adipamide/hexamethylene-azelaiamide/caprolactam (nylon6:6/6:9/6)

Also useful is nylon 6:3 produced by Dynamit Nobel. This polyamide isthe product of the dimethyl ester of terephthalic acid and a mixture ofisomeric trimethyl hexamethylenediamine. Another useful nylon is DuPont's Zytel® ST which is a nylon-based alloy.

Preferred nylons include nylon 6,6:6, 11, 12, 6:3 and 6:12.

The number average molecular weights of the polyamides used in theinvention are generally above about 10,000.

C. Engineering Thermoplastic Resin

The term "dissimilar engineering thermoplastic" refers to engineeringthermoplastics other than those encompassed by the polyamides of theinstant invention.

For purposes of the specification and claims, the term "engineeringthermoplastic resin" encompasses the various polymers found in theclasses listed in Table A below and thereafter defined in thespecification.

                  Table A                                                         ______________________________________                                        1.     Polyolefins                                                            2.     Thermoplastic polyesters                                               3.     Poly(aryl ethers) and Poly(aryl sulfones)                              4.     Polycarbonates                                                         5.     Acetal resins                                                          6.     Thermoplastic polyurethanes                                            7.     Halogenated thermoplastics                                             8.     Nitrile barrier resins                                                 ______________________________________                                    

The label engineering thermoplastic resin has come to be applied tothose polymers that possess a property balance comprising strength,stiffness, impact, and long term dimensional stability. Preferably theseengineering thermoplastic resins have glass transition temperatures orapparent crystalline melting points (defined as that temperature atwhich the modulus, at low stress, shows a catastrophic drop) of overabout 120° C, more preferably between about 150° C and about 350° C, andare capable of forming a continuous network structure through athermally reversible crosslinking mechanism. Such thermally reversiblecrosslinking mechanisms include crystallites, polar aggregations, ionicaggregations, lamellae, or hydrogen bonding. In a specific embodiment,where the viscosity of the block copolymer or blended block copolymercomposition at processing temperature Tp and a shear rate of 100 sec⁻¹is η, the ratio of the viscosity of the engineering thermoplasticresins, or blend of engineering thermoplastic resin with viscositymodifiers to η should be between about 0.2 and about 4.0, preferablyabout 0.8 and about 1.2. As used in the specification and claims, theviscosity of the block copolymer, polyamide and the thermoplasticengineering resin is the "melt viscosity" obtained by employing a pistondriven capillary melt rheometer at constant shear rate and at someconsistent temperature above melting, say 260° C. The upper limit (350°C) on apparent crystalline melting point or glass transition temperatureis set so that the resin may be processed in low to medium shear rateequipment at commercial temperature levels of 350° C or less.

The engineering thermoplastic resin includes also blends of variousengineering thermoplastic resins and blends with additional viscositymodifying resins.

These various classes of engineering thermoplastics are defined below.

1. Polyolefins

The polyolefins employed in the instant invention are crystalline orcrystallizable poly(alpha-olefins) and their copolymers. Thealpha-olefin or 1-olefin monomers employed in the instant invention have2 to 5 carbon atoms. Examples of particular useful polyolefins includelow density polyethylene, high density polyethylene, isotacticpolypropylene, poly(1-butene), poly(4-methyl-1-pentene), and copolymersof 4-methyl-1-pentene with linear or branched alpha-olefins. Acrystalline or crystallizable structure is important in order for thepolymer to be capable of forming a continuous structure with the otherpolymers in the polymer blend of the instant invention. The numberaverage molecular weight of the polyolefins is preferably above about10,000, more preferably above about 50,000. In addition, it is preferredthat the apparent crystalline melting point be above about 100° C,preferably between about 100° C and about 250° C, and more preferablybetween about 140° C and about 250° C. The preparation of these variouspolyolefins are well known. See generally "Olefin Polymers", Volume 14,Kirk-Othmer Encyclopedia of Chemical Technology, pages 217-335 (1967).

The high density polyethylene employed has an approximate cyrstallinityof over about 75% and a density in grams per cubic centimeter (g/cm³) ofbetween about 0.94 and 1.0 while the low density polyethylene employedhas an approximate crystallinity of over about 35% and a density ofbetween about 0.90 g/cm³ and 0.94 g/cm³. Most commercial polyethyleneshave a number average molecular weight of about 50,000 to about 500,000.

The polypropylene employed is the so-called isotactic polypropylene asopposed to atactic polypropylene. This polypropylene is described in theabove Kirk-Othmer reference and in U.S. Pat. No. 3,112,300. The numberaverage molecular weight of the polypropylene employed is typically inexcess of about 100,000. The polypropylene suitable for this inventionmay be prepared using methods of the prior art. Depending on thespecific catalyst and polymerization conditions employed, the polymerproduced may contain atactic as well as isotactic, syndiotactic orso-called stereo-block molecules. These may be separated, if desired, byselective solvent extraction to yield products of low atactic contentthat crystallize more completely. The preferred commercialpolypropylenes are generally prepared using a solid, crystalline,hydrocarbon-insoluble catalyst made from a titanium trichloridecomposition and an aluminum alkyl compound, e.g., triethyl aluminum ordiethyl aluminum chloride. If desired, the polypropylene employed may bea copolymer containing minor (1 to 20 percent by weight) amounts ofethylene or other alpha-olefin comonomers.

The poly(1-butene) preferably has an isotactic structure. The catalystsused in preparing the poly(1-butene) are typically organometalliccompounds commonly referred to as Ziegler-Natta catalysts. A typicalcatalyst is the interacted product resulting from mixing equimolarquantities of titanium tetrachloride and triethylaluminum. Themanufacturing process is normally carried out in an inert diluent suchas hexane. Manufacturing operations, in all phases of polymer formation,are conducted in such a manner as to guarantee rigorous exclusion ofwater even in trace amounts.

One very suitable polyolefin is poly(4-methyl-1-pentene).Poly(4-methyl-1-pentene) typically has an apparent crystalline meltingpoint of between about 240 and 250° C and a relative density of betweenabout 0.80 and 0.85. Monomeric 4-methyl-1-pentene is commerciallymanufactured by the alkali-metal catalyzed dimerization of propylene.The homopolymerization of 4-methyl-1-pentene with Ziegler-Nattacatalysts is described in the Kirk-Othmer Encyclopedia of ChemicalTechnology, Supplement volume, pages 789-792 (second edition, 1971).However, the isotactic homopolymer of 4-methyl-1-pentene has certaintechnical defects, such as brittleness and inadequate transparency.Therefore, commercially available poly(4-methyl-1-pentene) is actually acopolymer with minor proportions of other alpha-olefins, together withthe addition of suitable oxidation and melt stabilizer systems. Thesecopolymers are described in the Kirk-Othmer Encyclopedia of ChemicalTechnology, Supplement volume, pages 792-907 (second edition, 1971), andare available from Mitsui Chemical Company under the tradename TPX®resin. Typical alpha-olefins are linear alpha-olefins having from 4 to18 carbon atoms. Suitable resins are copolymers of 4-methyl-1-pentenewith from about 0.5 to about 30% by weight of a linear alpha-olefin.

If desired, the polyolefin may be a mixture of various polyolefins.However, the much preferred polyolefin is isotactic polypropylene.

2. Thermoplastic Polyesters

The thermoplastic polyesters employed in the instant invention have agenerally crystalline structure, a melting point over about 120° C, andare thermoplastic as opposed to thermosetting.

One particularly useful group of polyesters are those thermoplasticpolyesters prepared by condensing a dicarboxylic acid or the lower alkylester, acid halide, or anhydride derivatives thereof with a glycol,according to methods well-known in the art.

Among the aromatic and aliphatic dicarboxylic acids suitable forpreparing polyesters useful in the present invention are oxalic acid,malonic acid, succinic acid, glutaric acid, adipic acid, suberic acid,azelaic acid, sebacic acid, terephthalic acid, isophthalic acid,p-carboxyphenoacetic acid, p,p'-dicarboxydiphenyl,p,p'-dicarboxydiphenylsulfone, p-carboxyphenoxyacetic acid,p-carboxyphenoxypropionic acid, p-carboxyphenoxybutyric acid,p-carboxyphenoxyvaleric acid, p-carboxyphenoxyhexanoic acid,p,p'-dicarboxydiphenylmethane, p,p-dicarboxydiphenylpropane,p,p'-dicarboxydiphenyloctane, 3-alkyl-4-(β-carboxyethoxy)-benzoic acid,2,6-naphthalene dicarboxylic acid, 2,7-naphthalene dicarboxylic acid,and the like. Mixtures of dicarboxylic acids can also be employed.Terephthalic acid is particularly preferred.

The glycols suitable for preparing the polyesters useful in the presentinvention include straight chain alkylene glycols of 2 to 12 carbonatoms such as ethylene glycol, 1,3-propylene glycol, 1,6-hexyleneglycol, 1,10-decamethylene glycol, 1,12-dodecamethylene glycol and thelike. Aromatic glycols can be substituted in whole or in part. Suitablearomatic dihydroxy compounds include p-xylylene glycol, pyrocatechol,resorcinol, hydroquinone, or alkyl-substituted derivatives of thesecompounds. Another suitable glycol is 1,4-cyclohexane dimethanol. Muchpreferred glycols are the straight chain alkylene glycols having 2 to 4carbon atoms.

A preferred group of polyesters are poly(ethylene terephthalate),poly(propylene terephthalate), and poly(butylene terephthalate). A muchpreferred polyester is poly(butylene terephthalate). Poly(butyleneterephthalate), a crystalline copolymer, may be formed by thepolycondensation of 1,4-butanediol and dimethylterephthalate orterephthalic acid, and has the generalized formula: ##STR1## where nvaries from 70 to 140. The molecular weight of the poly(butyleneterephthalate) typically varies from about 20,000 to about 25,000. Asuitable process for manufacturing the polymer is disclosed in BritishPat. No. 1,305,130.

Commercially available poly(butylene terephthalate) is available fromGeneral Electric under the tradename VALOX® thermoplastic polyester.Other commercial polymers include CELANEX® from Celenese, TENITE® fromEastman Kodak, and VITUF® from Goodyear Chemical.

Other useful polyesters include the cellulosics. The thermoplasticcellulosic esters employed herein are widely used as molding, coatingand film-forming materials and are well known. These materials includethe solid thermoplastic forms of cellulose nitrate, cellulose acetate(e.g. cellulose diacetate, cellulose triacetate), cellulose butyrate,cellulose acetate butyrate, cellulose propionate, cellulosetridecanoate, carboxymethyl cellulose, ethyl cellulose, hydroxyethylcellulose and acetylated hydroxyethyl cellulose as described on pages25-28 of Modern Plastics Encyclopedia, 1971-72, and references listedtherein.

Another useful polyester is polypivalolactone. Polypivalolactone is alinear polymer having recurring ester structural units mainly of theformula:

    --CH.sub.2 --C(CH.sub.3).sub.2 C(O)O--

i.e., units derived from pivalolactone. Preferably the polyester is apivalolactone homopolymer. Also included, however, are the copolymers ofpivalolactone with not more than 50 mole percent, preferably not morethan 10 mole percent of other beta-propiolactones, such asbeta-propiolactone, alpha, alpha-diethyl-beta-propiolactone andalpha-methyl-alpha-ethyl-beta-propiolactone. The term"beta-propiolactones" refers to beta-propiolactone (2-oxetanone) and toderivatives thereof which carry no substituents at the beta-carbon atomof the lactone ring. Preferred beta-propiolactones are those containinga tertiary or quaternary carbon atom in the alpha position relative tothe carbonyl group. Especially preferred are the alpha,alpha-dialkyl-beta-propiolactones wherein each of the alkyl groupsindependently has from one to four carbon atoms. Examples of usefulmonomers are:

alpha-ethyl-alpha-methyl-beta-propiolactone,

alpha-methyl-alpha-isopropyl-beta-propiolactone,

alpha-ethyl-alpha-n-butyl-beta-propiolactone,

alpha-chloromethyl-alpha-methyl-beta-propiolactone,

alpha, alpha-bis(chloromethyl)-beta-propiolactone, and

alpha, alpha-dimethl-beta-propiolactone (pivalolactone).

See generally U.S. Pat. No. 3,259,607; U.S. Pat. No. 3,299,171; and U.S.Pat. No. 3,579,489. These polypivalolactones have a molecular weight inexcess of 20,000 and a melting point in excess of 120° C.

Another useful polyester is polycaprolactone. Typicalpoly(ε-caprolactones) are substantially linear polymers in which therepeating unit is ##STR2## These polymers have similar properties to thepolypivalolactones and may be prepared by a similar polymerizationmechanism. See generally U.S. Pat. No. 3,259,607.

3. Poly(aryl ethers) and Poly(aryl sulfones)

Various polyaryl polyethers are also useful as engineering thermoplasticresins. The poly(aryl polyethers) envisioned in the present inventioninclude the linear thermoplastic polymers composed of recurring unitshaving the formula

    --O--G--O--G')                                             I

wherein G is the residuum of a dihydric phenol selected from the groupconsisting of ##STR3## wherein R represents a bond between aromaticcarbon atoms, --O--, --S--, --S--S--, or divalent hydrocarbon radicalhaving from 1 to 18 carbon atoms inclusive, and G' is the residuum of adibromo or diiodobenzenoid compound selected from the group consistingof ##STR4## wherein R' represents a bond between aromatic carbon atoms,--O--, --S--, --S--S--, or a divalent hydrocarbon radical having from 1to 18 carbon atoms inclusive, with the provisions that when R is --O--,R' is other than --O--; when R' is --O--, R is other than --O--; when Gis II, G' is V, and when G' is IV, G is III. Polyarylene polyethers ofthis type exhibit excellent physical properties as well as excellentthermal oxidative and chemical stability. These poly(aryl polyethers)can be produced by the method disclosed in U.S. Pat. No. 3,332,909.Commercial poly(aryl polyethers) can be obtained from Uniroyal ChemicalDivision under the tradename ARYLON T® Polyarylethers, having a melttemperature of between about 280° C and 310° C.

Another group of useful engineering thermoplastic resins includearomatic poly(sulfones) comprising repeating units of the formula

    --Ar--SO.sub.2 --

in which Ar is a bivalent aromatic radical and may vary from unit tounit in the polymer chain (so as to form copolymers of various kinds).Thermoplastic poly(sulfones) generally have at least some units of thestructure ##STR5## in which Z is oxygen or sulphur or the residue of anaromatic diol such as a 4,4' bisphenol. One example of such apoly(sulfone) has repeating units of the formula ##STR6## another hasrepeating units of the formula ##STR7## and others have repeating unitsof the formula ##STR8## or copolymerized units in various proportions ofthe formula ##STR9## The thermoplastic poly(sulfones) may also haverepeating units having the formula ##STR10## These aromaticpoly(sulfones) and their method of preparation are disclosed in thevarious patent references cited in the first column of U.S. Pat. No.3,729,527.

Poly(ether sulfones) having repeating units of the following structure##STR11## can be prepared by the method disclosed in U.S. Pat. No.3,634,355; and are available from ICI United States Inc. as grades 200Pand 300P. ICI grade 200P has a glass transition temperature of about230° C.

Poly(ether sulfones) having repeating units of the following structure##STR12## are available from Union Carbide as UDEL® poly(sulfone) resin.

4. Polycarbonates

The polycarbonates utilized in the preparation of the blends of thisinvention are of the general formulae ##STR13## wherein Ar is selectedfrom the group consisting of phenylene and alkyl, alkoxyl, halogen andnitro-substituted phenylene; A is selected from the group consisting ofcarbon-to-carbon bonds, alkylidene, cycloalkylidene, alkylene,cycloalkylene, azo, imino, sulfur, oxygen, sulfoxide and sulfone, and nis at least two.

The preparation of the polycarbonates is well known and the detailsthereof need not be delineated herein. There are a variety ofpreparative procedures set forth in Chemistry and Physics ofPolycarbonates by Herman Schnell, Interscience Division of John Wiley &Co., New York (1964), first edition, as well as in British Pat. No.772,627 and U.S. Pat. No. 3,028,365. In general, a preferred reaction iscarried out by dissolving the dihydroxy component in a base such aspyridine and bubbling phosgene into the stirred solution at the desiredrate. Tertiary amines may be used to catalyze the reaction as well as toact as acid acceptors throughout the reaction. Since the reaction isnormally exothermic, the rate of phosgene addition can be used tocontrol the reaction temperature. The reactions generally utilizeequimolar amounts of phosgene and dihydroxy reactants, however, themolar ratios can be varied dependent upon the reaction conditions.

The preferred polycarbonate utilized in this invention is obtained whenAr is p-phenylene and A is isopropylidene. This polycarbonate isprepared by reacting para, para'-isopropylidenediphenol with phosgeneand is sold by General Electric Company under the trademark LEXAN® andby Mobay under the trademark MERLON®. This commercial polycarbonatetypically has a molecular weight of around 18,000, and a melttemperature of over 230° C. Other polycarbonates may be prepared byreacting other dihydroxy compounds, or mixtures of dihydroxy compounds,with phosgene. The dihydroxy compounds may include aliphatic dihydroxycompounds although for best high temperature properties aromatic ringsare essential. The dihydroxy compounds may include within the structurediurethane linkages. Also, part of the structure may be replaced bysiloxane linkage. These and other variations of polycarbonate structureare described in the Schnell reference cited above. The same referencepresents a long list of monomers (particularly dihydroxy compounds) thatmay be used in polycarbonate synthesis.

5. Acetal Resin

The acetal resins employed in the blends of the instant inventioninclude the high molecular weight polyacetal homopolymers made bypolymerizing formaldehyde, see MacDonald U.S. Pat. No. 2,768,944 (DuPont) or by polymerizing trioxane, see Bartz U.S. Pat. Nos. 2,947,727and 2,947,728. The literature on formaldehyde polymerization, synthesissteps and properties of useful acetal resins is summarized in theJournal of Applied Polymer Science, 1, 158-191 (1959). These polyacetalhomopolymers are commercially available from Du Pont under the tradenameDELRIN®. A related polyether-type resin is available from Hercules underthe tradename PENTON® and has the structure: ##STR14##

The acetal resin prepared from formaldehyde has a high molecular weightand a structure typified by the following:

    --H--O--CH.sub.2 --O--CH.sub.2 --O).sub.x H--

where terminal groups are derived from controlled amounts of water andthe x denotes a large (typically 1500) number of formaldehyde unitslinked in head-to-tail fashion. To increase thermal and chemicalresistance, terminal groups are typically converted to esters or ethers.

Also included in the term polyacetal resins are the polyacetalcopolymers, such as those listed in British Pat. No. 807,589 (Du Pont).These copolymers include block copolymers of formaldehyde with monomersor prepolymers of other materials capable of providing active hydrogens,such as alkylene glycols, polythiols, vinyl acetate - acrylic acidcopolymers, or reduced butadiene/acrylonitrile polymers.

Celanese has commercially available a copolymer of formaldehyde andethylene oxide under the tradename CELCON® that is useful in the blendsof the present invention. These copolymers typically have a structurecomprising recurring units having the formula ##STR15## wherein each R₁and R₂ is selected from the group consisting of hydrogen, lower alkyland lower halogen substituted alkyl radicals and wherein n is an integerfrom zero to three and wherein n is zero in from 85% to 99.9% of therecurring units. See U.S. Pat. No. 3,027,352; U.S. Pat. No. 3,072,609;and British Pat. No. 911,960.

Formaldehyde and trioxane can be copolymerized with an unlimited numberof other aldehydes, cyclic ethers, vinyl compounds, ketenes, cycliccarbonates, epoxides, isocyanate, ethers, and other compounds. Thesecompounds include ethylene oxide, 1,3-dioxolane, 1,3-dioxane,1,3-dioxepene, epichlorohydrin, propylene oxide, isobutylene oxide, andstyrene oxide.

6. Thermoplastic Polyurethanes

Polyurethanes, otherwise known as isocyanate resins, also can beemployed in this invention as long as they are thermoplastic as opposedto thermosetting. Some of these thermoplastic condensation polymers aredescribed on pages 106-108 of Modern Plastics Encyclopedia, 1971-72. Forexample, polyurethanes formed from toluene diisocyanate (TDI) ordiphenyl methane 4,4-diisocyanate (MDI) and a wide range of polyols,such as, polyoxyethylene glycol, polyoxypropylene glycol,hydroxy-terminated polyesters, polyoxyethylene-oxypropylene glycols aresuitable. The thermoplastic, normally solid polyrethanes described inSaunders & Frisch, "Polyurethanes: Chemistry and Technology,"Interscience Publishers, New York, Part I, Chemistry," published in 1963and Part II, "Technology," published in 1964 can be used.

These thermoplastic polyurethanes are avaible from K. J. Quinn Co. underthe tradename Q-THANE® and from Upjohn Co. under the tradenamePELLETHANE® CPR.

7. Halogenated Thermoplastics

Another group of useful engineering thermoplastics include thosehalogenated thermoplastics having an essentially crystalline structureand a melt point in excess of 120° C. These halogenated thermoplasticsinclude polytetrafluoroethylene, polychlorotrifluoroethylene,polybromotrifluoroethylene, poly(vinylidene fluoride) homopolymer andcopolymer, and poly(vinylidene chloride) homopolymer and copolymer.

Polytetrafluoroethylene (PTFE) is the name given to fully fluorinatedpolymers of the basic chemical formula --CF₂ --CF₂)_(n) which contain76% by weight fluorine. These polymers are highly crystalline and have acrystalline melting point of over 300° C. Commercial PTFE is availablefrom Du Pont under the tradename TEFLON® and from Imperial ChemicalIndustries under the tradename FLUON®. Polychlorotrifluoroethylene(PCTFE) and polybromotrifluoroethylene (PBTFE) are also available inhigh molecular weights and can be employed in the instant invention. Themethods for preparing PTFE, PCTFE, and PBTFE along with the polymerproperties are discussed in the Kirk-Othmer Encyclopedia of Science andTechnology, Volume 9, pages 805-847 (1966).

Especially preferred halogenated polymers are homopolymers andcopolymers of vinylidene fluoride. Poly(vinylidene fluoride)homopolymers are the partially fluorinated polymers of the chemicalformula --CH₂ --CF₂)_(n). These polymers are tough linear polymers witha crystalline melting point at 170° C. Commercial homopolymer isavailable from Pennwalt Chemicals Corporation under the tradenameKYNAR®. See Kirk-Othmer Encyclopedia of Science and Technology, Volume9, pages 840-847 (1966). The term "poly(vinylidene fluoride)" as usedherein refers not only to the normally solid homopolymers of vinylidenefluoride, but also to the normally solid copolymers of vinylidenefluoride containing at least 50 mole percent of polymerized vinylidenefluoride units, preferably at least about 70 mole percent vinylidenefluoride and more preferably at least about 90%. Suitable comonomers arehalogenated olefins containing up to 4 carbon atoms, for example, sym.dichlorodifluoroethylene, vinyl fluoride, vinyl chloride, vinylidenechloride, perfluoropropene perfluorobutadiene, chlorotrifluoroethylene,trichloroethylene, tetrafluoroethylene and the like. Methods ofsynthesizing vinylidene fluoride polymers are well known and many of thepolymers are available commercially. See generally U.S. Pat. No.3,510,429.

Another useful group of halogenated thermoplastics includepoly(vinylidene chloride) homopolymers and copolymers. Crystallinevinylidene chloride copolymers are especially preferred. The normallycrystalline vinylidene chloride copolymers that are useful in thepresent invention are those containing at least about 70 percent byweight of vinylidene chloride together with 30 percent or less of acopolymerizable monoethylenic monomer. Exemplary of such monomers arevinyl chloride, vinyl acetate, vinyl propionate, acrylonitrile, alkyland aralkyl acrylates having alkyl and aralkyl groups of up to about 8carbon atoms, acrylic acid, acrylamide, vinyl alkyl ethers, vinyl alkylketones, acrolein, allyl ethers and others, butadiene and chloropropene.Known ternary compositions also may be employed advantageously.Representative of such polymers are those composed of at least 70percent by weight of vinylidene chloride with the remainder made up of,for example, acrolein and vinyl chloride, acrylic acid andacrylonitrile, alkyl acrylates and alkyl methacrylates, acrylonitrileand butadiene, acrylonitrile and itaconic acid, acrylonitrile and vinylacetate, vinyl propionate, or vinyl chloride, allyl esters or ethers andvinyl chloride, butadiene and vinyl acetate, vinyl propionate, or vinylchloride and vinyl ethers and vinyl chloride. Quaternary polymers ofsimilar monomeric composition will also be known. Particularly usefulfor the purposes of the present invention, are copolymers of from about70 to about 95 percent by weight vinylidene chloride with the balancebeing vinyl chloride. Such copolymers may contain conventional amountsand types of plasticizers, stabilizers, nucleators and extrusion aids.Further, blends of two or more of such normally crystalline vinylidenechloride polymers may be used as well as blends comprising such normallycrystalline polymers in combination with other polymeric modifiers e.g.the copolymers of ethylene-vinyl acetate, styrene-maleic anhydride,styrene-acrylonitrile and polyethylene. See U.S. Pat. No. 3,983,080;U.S. Pat. No. 3,291,769; and U.S. Pat. No. 3,642,743.

8. Nitrile Barrier Resins

The nitrile barrier resins of the instant invention are thosethermoplastic materials having an alpha, beta-olefinically unsaturatedmononitrile content of 50% by weight or greater. These nitrile barrierresins may be copolymers, grafts of copolymers onto a rubbery substrate,or blends of homopolymers and/or copolymers.

The alpha, beta-olefinically unsaturated mononitriles encompassed hereinhave the structure ##STR16## where R is hydrogen, a lower alkyl grouphaving from 1 to 4 carbon atoms, or a halogen. Such compounds includeacrylonitrile, alphabromoacrylonitrile, alpha-fluoroacrylonitrile,methacrylonitrile, ethacrylonitrile, and the like. The most preferredolefinically unsaturated nitriles in the present invention areacrylonitrile and methacrylonitrile and mixtures thereof.

These nitrile barrier resins may be divided into several classes on thebasis of complexity. The simplest molecular structure is a randomcopolymer, predominantly acrylonitrile or methacrylonitrile. The mostcommon example is a styrene-acrylonitrile copolymer. Block copolymers ofacrylonitrile, in which long segments of polyacrylonitrile alternatewith segments of polystyrene, or of polymethyl methacrylate, are alsoknown.

Simultaneous polymerization of more than two comonomers produces aninterpolymer, or in the case of three components, a terpolymer. A largenumber of comonomers are known. These include lower alpha olefins offrom 2 to 8 carbon atoms, e.g., ethylene, propylene, isobutylene,butene-1, pentene-1, and their halogen and aliphatic substitutedderivatives as represented by vinyl chloride, vinylidene chloride, etc.;monovinylidene aromatic hydrocarbon monomers of the general formula:##STR17## wherein R₁ is hydrogen, chlorine or methyl and R₂ is anaromatic radical of 6 to 10 carbon atoms which may also containsubstituents such as halogen and alkyl groups attached to the aromaticnucleus, e.g., styrene, alpha methyl styrene, vinyl toluene, alphachlorostyrene, ortho chlorostyrene, para chlorostyrene, metachlorostyrene, ortho methyl styrene, para methyl styrene, ethyl styrene,isopropyl styrene, dichloro styrene, vinyl naphthalene, etc. Especiallypreferred comonomers are isobutylene and styrene.

Another group of comonomers are vinyl ester monomers of the generalformula: ##STR18## wherein R₃ is selected from the group conprisinghydrogen, alkyl groups of from 1 to 10 carbon atoms, aryl groups of from6 to 10 carbon atoms including the carbon atoms in ring substitutedalkyl substituents; e.g. vinyl formate, vinyl acetate, vinyl propionate,vinyl benzoate and the like.

Similar to the foregoing and also useful are the vinyl ether monomers ofthe general formula:

    H.sub.2 C═CH--O--R.sub.4

wherein R₄ is an alkyl group of from 1 to 8 carbon atoms, an aryl groupof from 6 to 10 carbons, or a monovalent aliphatic radical of from 2 to10 carbon atoms, which aliphatic radical may be hydrocarbon oroxygen-containing, e.g., an aliphatic radical with ether linkages, andmay also contain other substituents such as halogen, carbonyl, etc.Examples of these monomeric vinyl ethers include vinyl methyl ether,vinyl ethyl ether, vinyl n-butyl ether, vinyl 2-chloroethyl ether, vinylphenyl ether, vinyl isobutyl ether, vinyl cyclohexyl ether, p-butylcyclohexyl ether, vinyl ether or p-chlorophenyl glycol, etc.

Other comonomers are those comonomers which contain a mono- ordi-nitrile function. Examples of these include methylene glutaronitrile,(2,4-dicyanobutene-1), vinylidene cyanide, crotonitrile,fumarodinitrile, maleodinitrile.

Other comonomers include the esters of olefinically unsaturatedcarboxylic acids, preferably the lower alkyl esters of alpha,beta-olefinically unsaturated carboxylic acids and more preferred theesters having the structure ##STR19## wherein R₁ is hydrogen, an alkylgroup having from 1 to 4 carbon atoms, or a halogen and R₂ is an alkylgroup having from 1 to 2 carbon atoms. Compounds of this type includemethyl acrylate, ethyl acrylate, methyl methacrylate, ethylmethacrylate, methyl alpha-chloro acrylate, and the like. Most preferredare methyl acrylate, ethyl acrylate, methyl methacrylate and ethylmethacrylate.

Another class of nitrile barrier resins are the graft copolymers whichhave a polymeric backbone on which branches of another polymeric chainare attached or grafted. Generally the backbone is preformed in aseparate reaction. Polyacrylonitrile may be grafted with chains ofstyrene, vinyl acetate, or methyl methacrylate, for example. Thebackbone may consist of one, two, three, or more components, and thegrafted branches may be composed of one, two, three or more comonomers.

The most promising products are the nitrile copolymers that arepartially grafted on a preformed rubbery substrate. This substratecontemplates the use of a synthetic or natural rubber component such aspolybutadiene, isoprene, neoprene, nitrile rubbers, natural rubbers,acrylonitrile-butadiene copolymers, ethylene-propylene copolymers,chlorinated rubbers, etc., which are used to strengthen or toughen thepolymer. This rubbery component may be incorporated into the nitrilecontaining polymer by any of the methods which are well known to thoseskilled in the art, e.g., direct polymerization of monomers, graftingthe acrylonitrile monomer mixture onto the rubber backbone, physicaladmixtures of the rubbery component, etc. Especially preferred arepolymer blends derived by mixing a graft copolymer of the acrylonitrileand comonomer on the rubber backbone with another copolymer ofacrylonitrile and the same comonomer. The acrylonitrile-basedthermoplastics are frequently polymer blends of a grafted polymer and anungrafted homopolymer.

The methods of forming these various nitrile barrier resins and examplesof these resins can be found in the following patents:

    ______________________________________                                        U.S. Pat. Nos.    3,325,458                                                                     3,336,276                                                                     3,426,102                                                                     3,451,538                                                                     3,540,577                                                                     3,580,974                                                                     3,586,737                                                                     3,634,547                                                                     3,652,731                                                                     3,671,607                                                   British Patents   1,279,745                                                                     1,286,380                                                                     1,327,095                                                   ______________________________________                                    

Commercial examples of nitrile barrier resins include BAREX® 210 resinby Standard Oil of Ohio, an acrylonitrile-based high nitrile resincontaining over 65% nitrile, and Monsanto's LOPAC® resin containing over70% nitrile, three-fourths of it derived from methacrylonitrile.

D. Viscosity Modifiers

In order to better match the viscosity characteristics of thethermoplastic engineering resin, the polyamide and the block copolymer,it is sometimes useful to first blend the thermoplastic engineeringresin with a viscosity modifier before blending the resulting mixturewith the polyamide and block copolymer. Suitable viscosity modifiersshould have a relatively high viscosity, a melt temperature of overabout 230° C, and possess a viscosity that is not very sensitive tochanges in temperature. Examples of suitable viscosity modifiers includepoly(2,6-dimethyl-1,4-phenylene)oxide and blends ofpoly(2,6-dimethyl-1,4-phenylene)oxide with polystyrene.

The poly(phenylene oxides) included as possible viscosity modifiers maybe presented by the following formula ##STR20## wherein R₁ is amonovalent substituent selected from the group consisting of hydrogen,hydrocarbon radicals free of a tertiary alphacarbon atom,halohydrocarbon radicals having at least two carbon atoms between thehalogen atom and phenol nucleus and being free of a tertiaryalpha-carbon arom, hydrocarbonoxy radicals free of aliphatic, tertiaryalpha-carbon atoms, and halohydrocarbonoxy radicals having at least twocarbon atoms between the halogen atom and phenol nucleus and being freeof an aliphatic, tertiary alpha-carbon atom; R'₁ is the same as R₁ andmay additionally be a halogen; m is an integer equal to at least 50,e.g. from 50 to 800 and preferably 150 to 300. Included among thesepreferred polymers are polymers having a molecular weight in the rangeof between 6,000 and 100,000 preferably about 40,000. Preferably, thepoly(phenylene oxide) is poly(2,6-dimethyl-1,4-phenylene)oxide. Thesepoly(phenylene oxides) are described, for example, in U.S. Pat. No.3,306,874; U.S. Pat. No. 3,306,875; and U.S. Pat. No. 3,639,508.

Commercially, the poly(phenylene oxide) is available as a blend withstyrene resin. See U.S. Pat. No. 3,383,435 and U.S. Pat. No. 3,663,654.These blends typically comprise between about 25 and 50% by weightpolystyrene units, and are available from General Electric Company underthe tradename NORYL® thermoplastic resin. The preferred molecular weightwhen employing a poly(phenylene oxide)/polystyrene blend is betweenabout 10,000 and about 50,000, preferably around 30,000.

The amount of viscosity modifier employed depends primarily upon thedifference between the viscosities of the block copolymer and theengineering thermoplastic resin at the processing temperature Tp.Typical amounts range from about 0 to about 100 parts by weightviscosity modifier per 100 parts by weight engineering thermoplasticresin, preferably from about 10 to about 50 parts by weight per 100parts engineering thermoplastic resin.

E. Method of Forming Interlocking Networks

The various engineering thermoplastic resins, including the hereindescribed polyamides, are normally immiscible, that is, typical blendsproduce grossly heterogeneous mixtures with no useful properties. Byemploying the present block copolymers to stabilize the various polymerblends, non-delaminating compositions are formed. However, it is anessential aspect of the present invention that the various polymers canbe blended in such a way as to form co-continuous interlocking networks;i.e., where a continuous phase of one polymer would be thought of asfilling the voids of a continuous phase of the second polymer. Theinterlocking structure of the various polymers does not show gross phaseseparation such as would lead to delamination. Further, the blend is notso intimately mixed that there is molecular mixing or miscibility, norone in which the separate phases will lead to delamination.

Without wishing to be bound to any particular theory, it is consideredthat there are two general requirements for the formation of aninterlocking network. First, there must be a primary phase networkstable to the shearing field. This requirement is fulfilled by employingthe block copolymers of the instant invention having the capability ofself-crosslinking (network formation) and furthermore havingsufficiently high molecular weight to retain its network (domain)structure in processing. Second, the other polymers employed must becapable of some kind of chemical or physical crosslinks or otherintermolecular association to maintain a continuous phase in the blend.The polymer must possess sufficient fluidity to interlock with theprimary network in the blending process. This second requirement is metby the instant thermoplastic engineering resins, the blends of theseresins with the instant viscosity modifiers, and the instantpolyolefins.

There are at least two methods (other than the absence of delamination)by which the presence of an interlocking network can be shown. In onemethod, an interlocking network is shown when molded or extruded objectsmade from the blends of this invention are placed in a refluxing solventthat quantitatively dissolves away the block copolymer and other solublecomponents, and the remaining polymer structure (comprising thethermoplastic engineering resin and polyamide) still has the shape andcontinuity of the molded or extruded object and is intact structurallywithout any crumbling or delamination, and the refluxing solvent carriesno insoluble particulate matter. If these criteria are fulfilled, thenboth the unextracted and extracted phases are interlocking andcontinuous. The unextracted phase must be continuous because it isgeometrically and mechanically intact. The extracted phase must havebeen continuous before extraction, since quantitative extraction of adispersed phase from an insoluble matrix is highly unlikely. Finally,interlocking networks must be present in order to have simultaneouscontinuous phases. Also, confirmation of the continuity of theunextracted phase may be made by microscopic examination. In the presentblends containing more than two components, the interlocking nature andcontinuity of each separate phase may be established by selectiveextraction. For example, in a blend containing block copolymer,polypropylene, and nylon 6, the block copolymers may be first extractedby refluxing toluene, leaving the polypropylene and nylon phases. Thenthe nylon may be extracted by hydrochloric acid leaving thepolypropylene phase. Alternatively, the nylon may be extracted first andthen the block copolymer. See generally Japanese Pat. No. 1,017,989.Phase continuity and the interconnecting of holes may be microscopicallyexamined after each extraction.

In the second method, a mechanical property such as tensile modulus ismeasured and compared with that expected from an assumed system whereeach continuous isotropically distributed phase contributes a fractionof the mechanical response, proportional to its compositional fractionby volume. Correspondence of the two values indicates presence of theinterlocking network, whereas, if the interlocking network is notpresent, the measured value is different than that of the predictedvalue.

An important aspect of the present invention is that the relativeproportions of the various polymers in the blend can be varied over awide range. The relative proportions of the polymers are presented belowin parts by weight (the total blend comprising 100 parts):

    ______________________________________                                                      Preferred                                                                              Most Preferred                                         ______________________________________                                        Dissimilar Engineering                                                                        5 to 48    10 to 35                                           Thermoplastic                                                                 Block Copolymer 4 to 40     8 to 20                                           ______________________________________                                    

The polyamide is present in an amount greater than the amount of thedissimilar engineering thermoplastic, i.e., the weight ratio ofpolyamide to dissimilar engineering thermoplastic is greater than 1:1.Accordingly, the amount of polyamide may vary from about 30 parts byweight to about 91 parts by weight, preferably about 48 to about 70parts by weight. Note that the minimum amount of block copolymernecessary to achieve these blends may vary with the particularengineering thermoplastic.

The blending of the dissimilar engineering thermoplastic resin,polyamide and the block copolymer may be done in any manner thatproduces a blend which will not delaminate on processing, i.e., in anymanner that produces the interlocking network. For example, the resin,polyamide and block copolymer may be dissolved in a solvent common forall and coagulated by admixing in a solvent in which none of thepolymers are soluble. But more preferably, a particularly usefulprocedure is to intimately mix the polymers in the form of granulesand/or powder in a high shear mixer. "Intimately mixing" means to mixthe polymers with sufficient mechanical shear and thermal energy toensure that interlocking of the various networks is achieved. Intimatemixing is typically achieved by employing high shear extrusioncompounding machines such as twin screw compounding extruders andthermoplastic extruders having at least a 20:1 L/D ratio and acompression ratio of 3 or 4:1.

The mixing or processing temperature (Tp) is selected in accordance withthe particular polymers to be blended. For example, when melt blendingthe polymers instead of solution blending, it will be necessary toselect a processing temperature above the melting point of the highestmelting point polymer. In addition, as explained more fully hereinafter,the processing temperature may also be chosen so as to permit theisoviscous mixing of the polymers. Typically, the mixing or processingtemperature is between about 150° C and about 400° C. For blendscontaining poly(butylene terephthalate) Tp is preferably between about230° C and about 300° C.

Another parameter that is important in melt blending to ensure theformation of interlocking networks is matching the viscosities of theblock copolymer, polyamide and the dissimilar engineering thermoplasticresin (isoviscous mixing) at the temperature and shear stress of themixing process. The better the interdispersion of the engineering resinand polyamide in the block copolymer network, the better the chance forformation of co-continuous interlocking networks on subsequent cooling.Therefore, it has been found that when the block copolymer has aviscosity η poise at temperature Tp and shear rate of 100 sec⁻¹, it ismuch preferred that the viscosity of the engineering thermoplasticresin, blend containing such resin, and polyamide have a viscosity attemperature Tp and a shear rate of 100 sec⁻¹ such that the ratio of theviscosity of the block copolymer over the viscosity of the engineeringthermoplastic and/or polyamide be between about 0.2 and about 4.0,preferably between about 0.8 and about 1.2. Accordingly, as used herein,isoviscous mixing means that the viscosity of the block copolymerdivided by the viscosity of the other polymer or polymer blend at thetemperature Tp is between about 0.2 and about 4.0. It should also benoted that within an extruder, there is a wide distribution of shearrates. Therefore, isoviscous mixing can occur even though the viscositycurves of two polymers differ at some of the shear rates.

In some cases, the order of mixing the polymers is critical.Accordingly, one may choose to mix the block copolymer with thepolyamide or other polymer first, and then mix the resulting blend withthe dissimilar engineering thermoplastic, or one may simply mix all thepolymers at the same time. There are many variants on the order ofmixing that can be employed, resulting in the multicomponent blends ofthe instant invention. It is also clear that the order of mixing can beemployed in order to better match the relative viscosities of thevarious polymers.

The block copolymer or block copolymer blend may be selected toessentially match the viscosity of the engineering resin and/orpolyolefin. Optionally, the block copolymer may be mixed with a rubbercompounding oil or supplemental resin as described hereinbefore tochange the viscosity characteristics of the block copolymer.

The particular physical properties of the instant block copolymers areimportant in forming co-continuous interlocking networks. Specifically,the most preferred block copolymers of the instant invention whenunblended do not melt in the ordinary sense with increasing temperature,since the viscosity of these polymers is highly non-Newtonian and tendsto increase without limit as zero shear stress is approached. Further,the viscosity of these block copolymers is also relatively insensitiveto temperature. This rheological behavior and inherent thermal stabilityof the block copolymer enhances its ability to retain its network(domain) structure in the melt so that when the various blends are made,interlocking and continuous networks are formed.

The viscosity behavior of the instant thermoplastic engineering resins,and polyamides on the other hand, typically is more sensitive totemperature than that of the instant block copolymers. Accordingly, itis often possible to select a processing temperature Tp at which theviscosities of the block copolymer and dissimilar engineering resinand/or polyamide fall within the required range necessary to forminterlocking networks. Optionally, a viscosity modifier, as hereinabovedescribed, may first be blended with the engineering thermoplastic resinor polyamide to achieve the necessary viscosity matching.

F. Uses and Additional Components

The polymer blends of the instant invention may be compounded furtherwith other polymers, oils, fillers, reinforcements, antioxidants,stabilizers, fire retardants, antiblocking agents and other rubber andplastic compounding ingredients without departing from the scope of thisinvention.

Examples of various fillers that can be employed are in the 1971-1972Modern Plastics Encyclopedia, pages 240-247. Reinforcements are alsovery useful in the present polymer blends. A reinforcement may bedefined simply as the material that is added to a resinous matrix toimprove the strength of the polymer. Most of these reinforcing materialsare inorganic or organic products of high molecular weight. Variousexamples include glass fibers asbestos, boron fibers, carbon andgraphite fibers, whiskers, quartz and silica fibers, ceramic fibers,metal fibers, natural organic fibers, and synthetic organic fibers.Especially preferred are reinforced polymer blends of the instantinvention containing about 2 to about 80 percent by weight glass fibers,based on the total weight of the resulting reinforced blend. It isparticularly desired that coupling agents, such as various silanes, beemployed in the preparation of the reinforced blends.

The polymer blends of the instant invention can be employed in any usetypically performed by engineering thermoplastics, such as metalreplacements and those areas where high performance is necessary.

To illustrate the instant invention, the following illustrativeembodiments are given. It is to be understood, however, that theembodiments are given for the purpose of illustration only and theinvention is not to be regarded as limited to any of the specificmaterials or conditions used in the specific embodiments.

In the Illustrative Embodiments and Comparative Example, various polymerblends were prepared by mixing the polymers in a 11/4 inch SterlingExtruder having a Kenics Nozzle. The extruder has a 24:1 L/D ratio and a3.8:1 compression ratio screw.

The various materials employed in the blends are listed below:

1. Block copolymer -- a selectively hydrogenated block copolymeraccording to the present invention having a structure S-EB-S and blockmolecular weights of about 7,500-38,000-7,500.

2. Oil - Tufflo 6056 rubber extending oil.

3. Nylon 6 - PLASKON® 8207 polyamide from Allied Chemical.

4. Nylon 6-12 - ZYTEL® 158 polyamide from Du Pont.

5. Polypropylene - Shell's 5520 polypropylene, which is an essentiallyisotactic polypropylene having a melt flow index of about 5 (230°C/2.16kg).

6. Poly(butylene terephthalate) - General Electric's VALOX® 310 resin(PBT).

7. polycarbonate - MERLON® M-40 polycarbonate from Mobay.

8. Poly(ether sulfone) - ICI's 200 P.

9. polyurethane - PELLETHANE® CPR from Upjohn.

10. Polyacetal - DELRIN® 500 from Du Pont.

11. Poly(acrylonitrile-co-styrene) - BAREX® 210 from Standard Oil ofOhio.

12. Fluoropolymer - TEFZEL® 200 poly(vinylidene fluoride) copolymer fromDu Pont.

In all blends containing an oil component, the block copolymer and oilwere premixed prior to the addition of the other polymers.

Illustrative Embodiment I

In Illustrative Embodiment I, various polymer blends were preparedaccording to the present invention. In each case, the polymer blend waseasily mixed, and the extrudate was homogeneous in appearance. Further,in each case, the resulting polyblend had the desired continuous,interlocking networks as established by the criteria hereinabovedescribed.

The compositions, conditions and test results are presented below inTable 1. The compositions are listed in percent by weight.

    TABLE 1      Blend No. 14 15 16 17 39 42 43 52 61 75 76 81 82 97 98 99 100 101 102     103 104 105 106 112 113 177 178       Block Copolymer 4.2 8.3 12.5 25.0 4.3 13.0 25.5 5.8 11.2 13.0 26.0     15.0 30.0 15.0 30.0 15.0 30.015.030.0 15.0 30.0 15.0 30.0 12.5 25.0 15.0 3     0.0 Oil 0.8 1.7 2.5 5.0 0.7 2.0 4.5 1.2 2.8 2.0 4.0             2.5 5.0     Nylon 6 47.5 45.0 42.5 35.0 47.5 42.5 35.0 25.2  21.3 17.5 21.3 17.5     63.7 52.5 63.7 52.5 63.7 52.5 63.7 52.5 63.7 52.5 63.7 52.5 21.3 17.5     Nylon 6-12         43.0 Polypropylene 47.5 45.0 42.5 35.0    67.8 43.0     Poly(butylene terephthalate     47.5 42.5 35.0   63.7 52.5     21.3 17.5 Polycarbonate            63.7 52.5 21.3 17.5 Poly(ether     sulfone)                21.3 17.5 Polyurethane                    21.3     17.5 Polyacetal                        21.3 17.5 Poly(acrylonitrile-     co-styrene)                          63.7 52.5 Fluoropolymer          21.3 17.5 Mixing (Melt) Temperature (° C) 230 230 230 228     262 -- -- -- -- 250 250 260 268 262 262 284 290 280 290 233 238 248 246     234 236 245 234

Illustrative Embodiment II

In Illustrative Embodiment II, 100 parts by weight of the blend number52 from Illustrative Embodiment I was reinforced with 65.6 parts byweight PPG 1/4 inch glass fiber strands by melt blending the glassfibers with the polymer blend in the extruder at a temperature of about240° C. The resulting composition had the following properties:

    ______________________________________                                        Young's modulus ×10.sup.3, psi                                                                   1078                                                 Yield, psi               7280                                                 Tensile at Break, psi    7280                                                 Ultimate Elongation at Break, %                                                                        1.58                                                 Flex Modulus ×10.sup.3, psi                                                                       882                                                 Notched Izod Impact Strength,                                                                          1.27                                                 ft-lbs/inch                                                                   ______________________________________                                    

Illustrative Embodiment III

In Illustrative Embodiment III, glass reinforced blends similar to theone prepared in Illustrative Embodiment II were prepared, except thatall four major components plus the glass fiber were dry blended togetherat the same time instead of first preparing the polyblend and thenadding the glass fibers.

The various compositions, conditions and test results are presentedbelow in Table 2. In all cases, the resulting polyblends possessed thedesired interlocking network structure.

                  TABLE 2                                                         ______________________________________                                        Blend No         56          58                                               ______________________________________                                        Component, Parts by                                                           Weight                                                                        Block Copolymer  3.5         6.8                                              Oil              0.7         1.7                                              Nylon 6          15.0        --                                               Nylon 6-12       --          26.1                                             Polypropylene    41.0        26.1                                             Glass Fibers     39.8        39.2                                             Extrusion Temperature,                                                                         240         240                                              ° C                                                                    Properties                                                                    Young's Modulus ×                                                                        1086        801                                              10.sup.3                                                                      Yield, psi       7470        7670                                             Tensile at Break,                                                                              7470        7670                                             psi                                                                           Ultimate Elongation                                                                            1.21        1.78                                             at Break, %                                                                   Flex Modulus × 10.sup.3,                                                                 862         719                                              psi                                                                           Notched Izod     1.33        1.16                                             Impact Strength,                                                              ft-lbs/inch                                                                   ______________________________________                                    

Illustrative Embodiment IV

In Illustrative Embodiment IV, various polymer blends containing Nylon 6were prepared. This embodiment shows that the presence of the blockcopolymer is essential for the success of the instant invention. Allblends were prepared by mixing on the extruder at 230° C. Thecompositions are presented below in Table 3. (Note, some blends are alsopresented in Table 1)

Blends 18, 12 and 41 are presented for comparison purposes and containeither Nylon 6 by itself or Nylon 6 with polypropylene, while Blends14-17 and 43 reveal blends of the present invention having at least twocontinuous interlocking networks.

                                      TABLE 3                                     __________________________________________________________________________    Blend No.   18    12   14   15   16   17   41  43                             __________________________________________________________________________    Component, Parts by                                                            Weight                                                                        Block Copolymer                                                                          --    --   4.2  8.3  12.5 25.0 --  25.5                            Oil        --    --   0.8  1.7  2.5  5.0  --  4.5                             Nylon 6    100   50   47.5 45   42.5 35   50  35                              PBT        --    --   --   --   --   --   50  35                               Polypropylene                                                                           --    50   47.5 45   42.5 35   --  --                             Toluene Solubles                                                               Expected (% w)                                                                           0     0    5    10   15   30   0   30                              Found (% w)                                                                              1.2   3.1  4.9  10.7 14.0 28.3 0.4 29.2                           HCl Solubles                                                                   Expected (% w)                                                                           100   50   47.5 45.0 42.5 35   50  35                              Found (% w)                                                                              98.8  17.8 45.0 42.9 47.6 28.6 2.3 35.3                           __________________________________________________________________________

The presence (or absence) of a continuous interlocking network wasexamined by a selective extraction technique. In this technique, thepolymer blend is subjected to a 16-hour Soxhlet extraction with hotrefluxing toluene. Ideally, the hot toluene should extract the blockcopolymer and oil, but should not dissolve the PBT or nylon. Then theunextracted portion of the blend is placed in a vessel containing 6molar hydrochloric acid (HCl) and shaken for about 20 hours at roomtemperature. The HCl should dissolve the Nylon 6, but not thepolypropylene or PBT. The unextracted portion of the blend after eachextraction is weighed and the weight loss compared with the expectedvalues.

In Blend 18, 1.2% of the Nylon 6 was soluble in hot toluene compared toan expected 0% (well within the accuracy of the technique). Theremainder of the polymer completely dissolved in the HCl.

Extraction of blends 12 and 41 not containing any of the claimed blockcopolymer reveal the absence of continuous interlocking networks. InBlend 12, 3.1% of the blend was soluble in hot toluene compared to anexpected 0%, also well within the accuracy of the technique. However,only 17.8% of the extracted blend was soluble in HCl compared to anexpected 50%. This indicates that a large portion of nylon was soencapsulated in the polypropylene as to be inaccessible to the HCl,i.e., there was no continuous network of nylon that would be accessibleto the HCl. In Blend 41, 0.4% of the blend of PBT and Nylon 6 wassoluble in hot toluene compared to a theoretical 0%. However, only 2.3%of the extracted blend was soluble in HCl compared to an expected 50%,indicating a lack of a continuous interlocking networks since apparentlyonly a small portion of nylon was accessible to the HCl.

Contrary to the results in Blends 12 and 41, the extraction techniquereveals the presence of continuous interlocking networks in Blends 14-17and 43 wherein the block copolymer of the instant invention is employed.For example, in Blend 14, 4.2 parts by weight block copolymer isemployed. The toluene extracted 4.9% compared to an expected 5%, andmost significantly, the HCl extracted 47.5% compared to an expected45.0%, all within the accuracy of the technique. This indicates that thenylon was present as a continuous network since apparently all the nylonwas accessible to the HCl as would be expected from a completelyconnected phase. Similar results are shown for the other polymer blendsprepared according to the present invention.

Comparative Example 1

In the Comparative Example 1, various blends of Nylon 6 and otherengineering thermoplastics were prepared in the absence of the presentblock copolymer. The various blends are presented below in Table 4 alongwith individual remarks concerning the blend.

                                      TABLE 4                                     __________________________________________________________________________                      Wt. Ratio of                                                                          Processing                                                            Nylon 6 to                                                                            Temperature                                         Blend No.                                                                            Eng. Th.   Eng. Th.                                                                              (° C)                                                                          Comments                                    __________________________________________________________________________    12     Polypropylene                                                                            1:1     235     Grainy appear-                                                                ance                                        41     PBT        1:1     240     Weak melt                                                                     hand take off                               68     PBT        1:1     265     Not strandable                              110    Polycarbonate                                                                            1:3     270     Melt Fracture,                                                                Extreme Die                                                                   Swell Surging                               114    Polyurethane                                                                             3:1     240     Surging, grainy                             115    Polyacetal 3:1     230     Die swell,                                                                    Surging,                                                                      Melt Fracture                               116    PBT        3:1     245     Die Swell,                                                                    Slight Melt                                                                   Fracture                                    117    Polycarbonate                                                                            3:1     270     Surging, Gross                                                                Melt Fracture,                                                                Die Swell                                   118    Poly(ether sulfone)                                                                      3:1     300     Slight surging,                                                               Strand dimpling                                                               (cavitation)                                                                  Slight Melt                                                                   Fracture                                    121    Fluoropolymer                                                                            3:1     300     Surging extreme,                                                              knobby gross                                                                  profile                                     176    Poly(acrylonitrile-                                                           co-styrene)                                                                              1:3     250     No comparison                                                                 made                                        __________________________________________________________________________

What is claimed is:
 1. A composition comprising the admixture obtainedby initimately mixing about 4 to about 40 parts by weight of a blockcopolymer, about 5 to about 48 parts by weight of at least onedissimilar engineering thermoplastic, and a polyamide in a weight ratioof polyamide to dissimilar engineering thermoplastic of greater than1:1, so as to form a polyblend wherein at least two of the polymers haveat least partial continuous interlocked networks with each other andwherein:(a) said block copolymer comprises at least two monoalkenylarene polymer end blocks A and at least one substantially completelyhydrogenated conjugated diene polymer mid block B, said block copolymerhaving an 8 to 55 percent by weight monoalkenyl arene polymer blockcontent, each polymer block A having an average molecular weight ofbetween about 5,000 and about 125,000, and each polymer block B havingan average molecular weight of between about 10,000 and about 300,000;(b) said polyamide has a molecular weight in excess of about 10,000; and(c) said dissimilar engineering thermoplastic resin is capable offorming a continuous structure and is selected from the group consistingof polyolefins, thermoplastic polyesters, poly(aryl ethers), poly(arylsulfones), polycarbonates, acetal resins, thermoplastic polyurethanes,halogenated thermoplastics, and nitrile barrier resins.
 2. A compositionaccording to claim 1 wherein said block copolymer monoalkenyl arene isstyrene and said block copolymer conjugated diene is selected fromisoprene and butadiene.
 3. A composition according to claim 1 whereinsaid block copolymer has an ABA linear structure.
 4. A compositionaccording to claim 1 wherein said block copolymer has a branchedstructure.
 5. A composition according to claim 3 wherein said blockcopolymer is a selectively hydrogenated block copolymer of styrene andbutadiene, said butadiene having a 1,2 content of between about 35% and55%.
 6. A composition according to claim 1 wherein said polyamide isselected from the group consisting of nylon 6, 6:6, 11, 12, 6:3 and6:12.
 7. A composition according to claim 6 wherein said polyamide isnylon
 6. 8. A composition according to claim 6 wherein said polyamide isnylon 6:12.
 9. A composition according to claim 1 wherein saiddissimilar engineering thermoplastic is a thermoplastic polyester.
 10. Acomposition according to claim 9 wherein said thermoplastic polyester isprepared by condensing a dicarboxylic acid with a glycol.
 11. Acomposition according to claim 9 wherein said thermoplastic polyester ispoly(butylene terephthalate).
 12. A composition according to claim 1wherein said dissimilar engineering thermoplastic is a polyolefin.
 13. Acomposition according to claim 12 wherein said polyolefin is essentiallyisotactic polypropylene.
 14. A composition according to claim 1 whereinsaid dissimilar engineering thermoplastic is a poly(aryl ether) orpoly(aryl sulfone).
 15. A composition according to claim 1 wherein saiddissimilar engineering thermoplastic is a polycarbonate.
 16. Acomposition according to claim 1 wherein said dissimilar engineeringthermoplastic is an acetal resin.
 17. A composition according to claim 1wherein said dissimilar engineering thermoplastic is a thermoplasticpolyurethane.
 18. A composition according to claim 1 wherein saiddissimilar enginerring thermoplastic is a halogenated thermoplastic. 19.A composition according to claim 18 wherein said halogenatedthermoplastic is crystalline polyvinylidene difluoride.
 20. Acomposition according to claim 1 wherein said dissimilar engineeringthermoplastic is a nitrile barrier resin.
 21. A composition according toclaim 20 wherein said nitrile barrier resin has an alpha,beta-olefinically unsaturated mononitrile content of at least 50% byweight.
 22. A composition according to claim 1 which contains about 2 toabout 80 percent by weight glass fibers.
 23. A composition according toclaim 1 wherein the block copolymer, polyolefin, and dissimilarengineering thermoplastic are melt blended under essentially isoviscousblending conditions.
 24. A composition comprising the admixture obtainedby intimately mixing about 4 to about 40 parts by weight of a blockcopolymer, about 5 to about 48 parts by weight of at least onedissimilar engineering thermoplastic, and a polyamide in a weight ratioof polyamide to dissimilar engineering thermoplastic of greater than 1:1under essentially isoviscous melt blending conditions so as to form apolyblend wherein at least two of the polymers have at least partialcontinuous interlocked networks with each other and wherein:(a) saidblock copolymer comprises at least two monoalkenyl arene polymer endblocks A and at least one substantially completely hydrogenatedconjugated diene polymer mid block B, said block copolymer having an 8to 55 percent by weight monoalkenyl arene polymer block content, eachpolymer block A having an average molecular weight of between about5,000 and about 125,000, and each polymer block B having an averagemolecular weight of between about 10,000 and about 300,000; (b) saidpolyamide has a molecular weight in excess of about 10,000; and (c) saiddissimilar engineering thermoplastic resin is capable of forming acontinuous structure and is selected from the group consisting ofpolyolefins, thermoplastic polyesters, poly(aryl ethers), poly(arylsulfones), polycarbonates, acetal resins, thermoplastic polyurethanes,halogenated thermoplastics, and nitrile barrier resins.
 25. Acomposition according to claim 24 wherein the viscosity ratio of theviscosity of the block copolymer divided by the viscosity of thepolyamide, dissimilar engineering thermoplastic, or mixture of polyamideand dissimilar engineering thermoplastic is between about 0.2 and about4.0 at the processing temperature Tp.
 26. A composition according toclaim 25 wherein said viscosity ratio is between about 0.8 and about1.2.
 27. A composition according to claim 25 wherein said processingtemperature Tp is between about 150° C and about 400° C.
 28. Acomposition according to claim 1 which contains between about 10 andabout 100 parts by weight of a viscosity modifier per 100 parts byweight of said dissimilar engineering thermoplastic.
 29. A compositionaccording to claim 28 wherein the viscosity modifier is selected fromthe group consisting of poly(2,6-dimethyl-1,4-phenylene)oxide and blendsof poly(2,6-dimethyl-1,4-phenylene)oxide with polystyrene.
 30. Acomposition according to claim 1 which contains about 2 to about 80percent by weight of a filler.
 31. A composition according to claim 1which contains about 2 to about 80 percent by weight of a reinforcement.